Patient Positioning and Anesthesia
By Ronald Ombaka Esq.
• Patient positioning is a major responsibility that is
shared by the entire operating room team. A balance
between optimal surgical positioning and patient
well-being is sometimes required.
• It is prudent to adapt optimal positioning as it can
pre-empt adverse outcomes.
• Many patient positions that are used for
surgery result in undesirable physiologic
– significant cardiovascular and respiratory
• Anesthetics blunt natural compensatory
mechanisms , rendering surgical patients
vulnerable to positional changes.
• Anesthesiologists play a critical role for the
proper positioning of patients in the operating
– Primarily because positions deemed optimal for
surgery often result in undesirable physiologic
changes putting surgical intervention at cross
purposes with patient safety.
• The goal (ideally)
– Whenever possible, patients should be placed in a
position that they would tolerate when awake.
• Surgeons wish to have optimal exposure, and
positions may be maintained for long periods.
• The duration of more extreme positions, if such
are necessary, should be limited as much as
• Expected tilting of the operating room table
during surgery should be anticipated before
draping, and the patient should be secured
• Use of safety straps and prevention of a patient
fall are fundamental.
• Complex arterial, venous, and cardiac
physiologic responses have evolved to blunt
the effects of positional changes on arterial
blood pressure and maintain perfusion to vital
– This is particularly important for humans who maintain an upright posture, owing to the
vertical distance from the heart to the brain and its need for constant perfusion.
• Normally, as an individual reclines from an
erect to a supine position, venous return to
the heart increases as pooled blood from the
lower extremities redistributes toward the
– Preload ↑
– stroke volume ↑
– cardiac output ↑
• Increase in arterial blood pressure activates afferent baroreceptors
– carotid sinuses
• Resulting in
– decreased sympathetic outflow
– increase parasympathetic impulses
• Ultimately = compensatory
– decrease in heart rate
– stroke volume
– cardiac output
• Mechanoreceptors from the atria and ventricle also are activated to
decrease sympathetic outflow to muscle and splanchnic vascular beds.
• Atrial reflexes are activated to regulate renal sympathetic nerve activity,
plasma renin, atrial natriuretic peptide, and arginine vasopressin levels.
• As a result, systemic arterial blood pressure is maintained within a narrow
range during postural changes in the unanesthetized setting.
• General anesthesia, muscle relaxation,
positive-pressure ventilation, and neuraxial
blockade interfere with autoregulatory
mechanisms, rendering patients under
anesthesia especially vulnerable to relatively
uncompensated circulatory effects of changes
• Positive-pressure ventilation
– ↑ mean intrathoracic pressure,
– ↓ venous return
– ↓ cardiac output
• Positive end-expiratory pressure increases mean
intrathoracic pressure further, as do conditions
associated with low lung compliance, such as
– Airways disease
– Light anesthesia.
• As such , arterial blood pressure is often
particularly labile at induction and during patient
(It is crucial for the anesthesiologist to anticipate, monitor, and treat these effects, and
to assess the safety of positional changes for each patient.)
• Interruptions in monitoring to facilitate
positioning or turning of the operating room
table must be minimized during this dynamic
• Patient positioning is always secondary to patient
• Anesthetized patients who are breathing
– ↓ tidal volume
– ↓functional residual capacity
– ↑ closing volume
(Positive-pressure ventilation with muscle relaxation may ameliorate ventilation-
perfusion mismatches )
• Any position that limits movement of the
diaphragm, chest wall, or abdomen may
increase atelectasis and intrapulmonary shunt.
• For instance when an individual shifts from
standing to supine,
– functional residual capacity decreases owing to
cephalad displacement of the diaphragm.
– The relative contribution to ventilation of the
chest wall compared with the diaphragm
decreases from 30% to 10%.
• The preferential perfusion of the dependent
portions of lung is dominated by gravity.
Supine(dorsal decubitus position)
• Because the entire body is close to the level of the heart,
hemodynamic reserve is best maintained.
• Because compensatory mechanisms are blunted by anesthesia,
however, even a few degrees of head-down (Trendelenburg)
position or head-up (reverse Trendelenburg) position are sufficient
to cause significant cardiovascular changes.
Associated Arm Position
• In a supine patient, one or both arms may be abducted out to the
side or adducted (tucked) alongside the body.
• It is recommended that upper extremity abduction be limited to
less than 90 degrees to minimize the likelihood of brachial plexus
injury by caudad pressure in the axilla from the head of the
• The hand and forearm are either supinated or
kept in a neutral position with the palm
toward the body to reduce external pressure
on the spiral groove of the humerus and the
• The elbows and any protruding objects, such
as intravenous fluid lines and stopcocks, are
Arm position on arm board. Abduction of arm should be limited to less than 90
degrees whenever possible. The arm is supinated, and the elbow is padded.
• Variations of the Supine Position
– Lawn chair position
Trendelenburg position and reverse
Trendelenburg position. Shoulder braces
should be avoided to prevent brachial plexus
Tilting a supine patient head down, the
Trendelenburg position, is often used to
increase venous return during hypotension, to
improve exposure during abdominal and
laparoscopic surgery, and to prevent air emboli
and facilitate cannulation during central line
Nonsliding mattresses are recommended
to prevent the patient from sliding cephalad.
Shoulder braces are not recommended
because of considerable risk of compression
injury to the brachial plexus
• The Trendelenburg position has significant cardiovascular and respiratory
– The head-down position
– Increases central venous, intracranial, and intraocular pressures.
• Prolonged head-down position also can lead to swelling of the face,
larynx, and tongue with an increased potential for postoperative
upper airway obstruction.
• The cephalic movement of abdominal viscera against the diaphragm also
decreases functional residual capacity and pulmonary compliance.
In spontaneously ventilating patients, the work of breathing increases.
• In mechanically ventilated patients, airway pressures must be higher to
ensure adequate ventilation.
• The stomach also lies above the glottis. Endotracheal intubation is often
preferred to protect the airway from pulmonary aspiration related to
reflux and to reduce atelectasis.
• Because of the risk of edema to the trachea and mucosa surrounding the
airway during surgeries in which patients have been in the Trendelenburg
position for prolonged periods, it may be prudent to verify an air leak
around the endotracheal tube or visualize the larynx before extubation.
• Reverse Trendelenburg position (head-up tilt) is often employed to
facilitate upper abdominal surgery by shifting the abdominal
• This position is increasingly popular because of the growing number
of laparoscopic surgeries.
• Caution is advised to prevent patients from slipping on the table,
and more frequent monitoring of arterial blood pressure may be
prudent to detect hypotension owing to decreased venous return.
• In addition, the position of the head above the heart reduces
perfusion pressure to the brain and should be taken into
consideration when determining optimal blood pressure.
(In all positions in which the head is at a different level than the heart, the
effect of the hydrostatic gradient on cerebral arterial and venous pressures
should be carefully considered in terms of cerebral perfusion pressure.
Careful documentation of any potential arterial pressure gradients is
• The Lawn chair position
– It better tolerated by patients who are awake or
undergoing monitored anesthesia care.
• In addition, because the legs are slightly above
the heart, venous drainage from the lower
extremity is facilitated.
• Also, the xiphoid to pubic distance is decreased,
reducing the tension on the ventral abdominal
musculature and easing closure of laparotomy
• The frog-leg position
– allows access to the perineum, medial thighs,
• Care must be taken to minimize stress and
postoperative pain in the hips and prevent
dislocation by supporting the knees
(Supine position and its analogues)
• Pressure alopecia
(Lumps, such as those caused by monitoring cable connectors, should
not be placed under head padding because they may create focal areas
(as the normal lumbar lordotic curvature, particularly the tone of the
paraspinous musculature, is lost during general anesthesia with muscle
relaxation or a neuraxial block.)
• Tissues overlying all bony prominences, such as
the heels and sacrum, must be padded to prevent
soft tissue ischemia owing to pressure, especially
during prolonged surgery.
• Peripheral nerve injury (Ulnar neuropathy is the most
– Regardless of the position of the upper extremities,
maintaining the head in a relatively midline position can
help minimize the risk of stretch injury to the brachial
NB: When patients are very heavy, caution is
advised when placing them in reverse axis on
the operating room table.
• The classic lithotomy position is frequently
used during gynecologic, rectal, and urologic
• Initiation of the lithotomy position requires
coordinated positioning of the lower
extremities by two assistants to avoid torsion
of the lumbar spine.
• Both legs should be raised together, flexing
the hips and knees simultaneously.
• The lower extremities should be padded to
prevent compression against the stirrups.
• After the surgery, the patient must be
returned to the supine position in a
(In essence an exact reversal of the initial positioning process)
Improper position of arms in lithotomy position with fingers at risk for compression
when the lower section of the bed is raised.
• When the legs are elevated, preload increases, causing a transient
increase in cardiac output and, to a lesser extent, cerebral venous
and intracranial pressure in otherwise healthy patients.
• In addition, the lithotomy position causes the abdominal viscera to
displace the diaphragm cephalad, reducing lung compliance and
potentially resulting in a decreased tidal volume.
• If obesity or a large abdominal mass is present (tumor, gravid
uterus), abdominal pressure may increase significantly enough to
obstruct venous return to the heart.
• Lastly, the normal lordotic curvature of the lumbar spine is lost in
the lithotomy position, potentially aggravating any previous lower
• Lower extremity compartment syndrome
• The lateral decubitus position is used most frequently for surgery
involving the thorax, retroperitoneal structures, or hip.
• The patient’s head must be kept in a neutral position to prevent
excessive lateral rotation of the neck and stretch injuries to the
(Additional head support may be required )
• The dependent ear should be checked to avoid folding and undue
• It is advised to verify that the eyes are securely taped before
repositioning if the patient is asleep.
• The dependent eye must be checked frequently for external
• Watch for compression of the dependent axillary structures.
(Regardless of the technique, the pulse should be monitored in the
dependent arm for early detection of compression to axillary
• Vascular compression and venous engorgement in the dependent
arm may affect the pulse oximetry reading, and a low saturation
reading may be an early warning of compromised circulation.
• When a kidney rest is used, it must be properly placed under the
dependent iliac crest to prevent inadvertent compression of the
inferior vena cava.
• Finally, a pillow or other padding is generally placed
between the knees with the dependent leg flexed to minimize
excessive pressure on bony prominences and stretch of low
• The lateral decubitus position also is associated with pulmonary
compromise. In a patient who is mechanically ventilated,
– lateral weight of the mediastinum
– disproportionate cephalad pressure of abdominal contents on the
dependent lung favors overventilation of the nondependent lung
– pulmonary blood flow to the underventilated,dependent lung
increases owing to the effect of gravity.
– ventilation-perfusion matching worsens
NB:Patients may be flexed while in the lateral position to
spread the ribs during thoracotomies or improve exposure of the
retroperitoneum for renal surgeries. The point of flexion, and the
kidney rest if raised, should lie under the iliac crest rather than
the flank or ribcage to minimize compression of the dependent
• This position is often accompanied by a
component of reverse Trendelenburg
positioning, creating the potential for venous
pooling in the lower body
• used primarily for surgical access to the
posterior fossa of the skull, the posterior
spine, the buttocks and perirectal area, and
the lower extremities.
• As with the supine position, if the legs are in
plane with the torso, hemodynamic reserve is
• Pulmonary function may be superior to the
supine or lateral decubitus positions if there is
no significant abdominal pressure and the
patient is properly positioned.
• The legs should be padded and flexed slightly
at the knees and hips. The head may be
supported face-down with its weight borne by
the bony structuresor turned to the side.
• Both arms may be positioned to the patient’s
sides and tucked in the neutral position or
placed next to the patient’s head on arm
boards—sometimes called the prone
• Extra padding under the elbow is needed to
prevent compression of the ulnar nerve.
• The arms should not be abducted greater
than 90 degrees to prevent excessive
stretching of the brachial plexus.
• Finally, elastic stockings and active
compressiondevices are needed for the lower
extremities to minimize pooling of the blood,
especially with any flexion of the body.
• When general anesthesia is planned, the patient is first
intubated on the stretcher, and all intravascular access is
obtained as needed.
• The endotracheal tube is well secured to prevent
dislodgment and loosening of tape owing to drainage of
saliva when prone.
• With the coordination of the entire operating room
staff(minimum of 5), the patient is turned prone onto the
operating room table, keeping the neck in line with the
spine during the move.
The anesthesiologist is primarily responsible for coordinating
the move and forrepositioning of the head.
• It is recommended to disconnect blood
pressure cuffs and arterial and venous lines
that are on the side that rotates furthest to
• Full monitoring should be reinstituted as
rapidly as possible.
• Endotracheal tube position and adequate
ventilation are reassessed immediately after
• Patients with cervical arthritis or
cerebrovascular disease, lateral rotation of the
neck may compromise carotid or vertebral
arterial blood flow or jugular venous drainage.
• Regardless of the technique employed to
support the head, the eyes, face, and airway
must be checked periodically to ensure that
the weight is borne only by the bony
structures, and that there is no pressure on
• Proper position is verified frequently and
noted in the anesthetic record.
• Because the abdominal wall is easily displaced,
external pressure on the abdomen may elevate intra-
abdominal pressure in the prone position.
• External pressure on the abdomen may push the
diaphragm cephalad, decreasing functional residual
capacity and pulmonary compliance, and increasing
peak airway pressure.
• Abdominal pressure also may impede venous return
through compression of the inferior vena cava
• As such careful attention must be paid to the ability of
the abdomen to hang free and to move with
• To prevent tissue injury, pendulous structures
(e.g., male genitalia and female breasts)
should be clear of compression; the breasts
should be placed medial to the bolsters.
• The prone position presents special risks for
morbidly obese patients, whose respiration is
already compromised, and who may be
difficult to reposition quickly.
• Sometimes it may be necessary to discuss
alternative positioning options with the
surgeon to ensure patient safety.
• The sitting position
( although infrequently used because of the perception of risk from venous
and paradoxical air embolism, offers advantages to the surgeon in
approaching the posterior cervical spine and the posterior fossa.)
• The main advantages of the sitting position over the
prone position for neurosurgical and cervical spine
– excellent surgical exposure
– decreased blood in the operative field
– reduced perioperative blood loss.
– superior access to the airway, reduced facial swelling, and
improved ventilation, particularly in obese patients.(to the
• The head may be fixed in pins for neurosurgery or
taped in place with adequate support for other
• arms must be supported to the point of slight
elevation of the shoulders to avoid traction on
the shoulder muscles and potential stretching of
upper extremity neurovascular structures.
• The knees are usually slightly flexed for balance
and to reduce stretching of the sciatic nerve, and
the feet are supported and padded.
• Because of the pooling of blood into the lower
body under general anesthesia patients are
particularly prone to hypotensive episodes.
• Head and neck position has been associated with complications
during surgery to the posterior spine or skull in the sitting position.
• Excessive cervical flexion has numerous adverse consequences.
– It can impede arterial and venous blood flow, causing hypoperfusion
or venous congestion of the brain.
– It may impede normal respiratory excursion.
– Excessive flexion also can obstruct the endotracheal tube and place
significant pressure on the tongue, leading to macroglossia.
(Generally, maintaining at least two fingers’ distance between the mandible and the
sternum is recommended for a normal-sized adult, and patients should not be
positioned at the extreme of their range of motion.)
• Because of the elevation of the surgical field
above the heart, and the inability of the dural
venous sinuses to collapse because of their bony
attachments, the risk of venous air embolism is a
• Arrhythmia, desaturation, pulmonary
hypertension, circulatory compromise, or cardiac
arrest may occur if sufficient quantities are